JP5914717B2

JP5914717B2 - Heat sink including a base plate structure having a periodic pattern, and related apparatus and method (heat sink including a base plate structure having a periodic pattern)

Info

Publication number: JP5914717B2
Application number: JP2015039193A
Authority: JP
Inventors: ブルース・アール・アルチャンボー; エリック・エヌ・チカンド; サミュエル・アール・コナー; ジョン・エス・マース
Original assignee: レノボ・エンタープライズ・ソリューションズ（シンガポール）プライベート・リミテッド
Priority date: 2009-08-06
Filing date: 2015-02-27
Publication date: 2016-05-11
Anticipated expiration: 2030-08-03
Also published as: JP2011040742A; TWI440425B; TW201112938A; CN101996963B; CN101996963A; JP5765897B2; US7848108B1; JP2015135979A; KR20110014956A

Description

The present invention relates to reducing the propagation of electromagnetic interference, and in particular to reducing the propagation of electromagnetic interference in the context of an integrated circuit heat sink.

Electromagnetic interference (EMI) is a disturbance from electromagnetic radiation that adversely affects electrical circuits. This disturbance may block, prevent, or otherwise reduce or limit the effective execution of the circuit. Undesirable electromagnetic radiation often begins in an integrated circuit (IC) and is emitted by other structures at a sufficient level to cause interference with other components. Specifically, heat sinks can be a problem. Because of its large metal surface area, the heat sink can serve as an efficient antenna for propagating electromagnetic radiation.

There are a number of ways known in the art to reduce EMI. One way to reduce EMI is to use a bypass or “decoupling” capacitor on each active device. A decoupling capacitor is connected between the poles of the power supply as close as possible to the active device. Another method known to reduce noise is to control the rise time of high speed signals. The rise time can be controlled using, for example, a series resistor. VCC filtering can also be used to reduce the amount of radio frequency interference that spreads through the power connection. Although additional components such as RF gaskets need to be added, shields can also be used.

As a result of the increase in clock speed and data rate of integrated circuits above 1 GHz, the wavelength of radiation emitted from the IC has dimensions comparable to the physical dimensions of IC heat sinks. This contributes to the efficiency of the heat sink acting as an antenna for noise on the IC / IC package. Although there are multiple heat sink grounding schemes that attempt to solve this problem, these measures increase the cost of the printed circuit board assembly and also use a significant portion of the limited space on the circuit board.

An object of the present invention is to improve the contents described in the background art.

A first embodiment of the present invention comprises a periodic pattern structure comprising an array of electrically conductive / thermally conductive patches spaced in two dimensions of a reference plane and having a thickness perpendicular to the reference plane. A heat sink including a base having the same. Multiple branches structurally connect the patches. Each branch connects adjacent patches, and has a width smaller than the width of each adjacent patch in the reference plane. A plurality of thermally conductive cooling fins are coupled to the base and extend perpendicular to the reference plane.

The second embodiment is an apparatus having a printed circuit board that includes a continuous electrically conductive layer.
A processor is physically coupled to the printed circuit board and electrically coupled to the electrically conductive layer. A heat sink is coupled to the circuit board in thermal contact with the processor. The heat sink includes a base having a periodic pattern structure including an array of electrically conductive / thermally conductive patches spaced in parallel to the conductive layer and having a thickness perpendicular to the conductive layer. Multiple branches structurally connect the patches. Each branch extends across the opening between two adjacent patches and has a width that is narrower than the width of each adjacent patch in the reference plane. A plurality of thermally conductive cooling fins are coupled to the base and extend perpendicular to the reference plane.

The third embodiment is a method for reducing propagation of electromagnetic noise generated by a microprocessor. Identify the frequency band of electromagnetic noise generated by the microprocessor. A periodic pattern of spaced patches, interconnected by branches, having a geometric arrangement with stopbands within the identified frequency bands is selected. The processor is in thermal contact with a heat sink having a base comprising an electrically conductive / thermally conductive material having a selected periodic pattern.

1 is a perspective view of a heat sink according to an embodiment of the present invention. FIG. FIG. 3 is a perspective view of a heat sink base showing the periodic pattern structure of the heat sink base in more detail. FIG. 3 is a perspective view of a heat sink base showing the periodic pattern structure of the heat sink base in more detail. FIG. 6 is a top view of a heat sink base showing the addition of a thermally / non-electrically conductive filler into the opening. 1 is a dimensioned top view of a heat sink base according to one particular exemplary embodiment. FIG. FIG. 6 is a top view with dimensions of a first portion of the heat sink base of FIG. 5. FIG. 6 is a dimensioned top view of a second portion of the heat sink base of FIG. 2 is a side view of an electronic device that includes a heat sink for cooling the CPU. FIG. FIG. 9 is an enlarged detail view of a portion of the electronic device of FIG. FIG. 6 is a graph showing the use of a heat sink base according to an embodiment of the present invention with a periodic pattern resulting in reduced EMI compared to a conventional solid heat sink base. 2 is a flow diagram illustrating an overview of a method according to an embodiment of the present invention for reducing propagation of electromagnetic noise generated by a processor on a circuit board.

Embodiments of the present invention relate to electromagnetic interference (EM) caused by integrated circuits (ICs) in electronic devices.
The object is to reduce I). One embodiment is a heat sink for an IC that includes a periodic pattern structure in the base of the heat sink. This periodic pattern structure, together with a solid metal layer (eg, ground layer or power supply layer) on the circuit board, forms an electromagnetic bandgap (EBG) structure that reduces the efficiency of the heat sink acting as an antenna in a certain frequency band. The periodic pattern structure includes a periodic array of electrically conductive patches interconnected by electrically conductive branches. In the opening of the periodic pattern structure, EB
A thermally / non-electrically conductive filler is filled that maximizes heat transfer in the heat sink without compromising the electrical properties of the G structure. The heat sink base uses a thermally / non-electrically conductive binder that maximizes heat transfer from the heat sink base to the fin while electrically insulating the fin from the heat sink base. Fins are joined. The physical parameters of the periodic pattern structure can be selected to reduce the propagation of electromagnetic waves in one or more characteristic bands. Although this heat sink thus reduces noise, it has a level of heat dissipation and cost comparable to conventional heat sinks.

The various materials described herein are optionally identified as electrically conductive or non-electrically conductive, and thermally conductive or non-thermally conductive. Virtually all materials can conduct heat and electricity to some extent, depending on the circumstances, but some materials are sufficient to be considered electrical conductors for the purposes of the present invention. Does not conduct electricity. Similarly, some materials do not conduct heat well enough to be considered thermal conductors for the purposes of the present invention. Thus, in the context of the present invention, a material is considered to be electrically conductive if it has an electrical conductivity of at least about 107 S / m, and it has a thermal conductivity of at least about 1 W / m · K. Considered sex. Although explicitly defined herein for clarity, these definitions of thermal conductivity and electrical conductivity are consistent with operational definitions known to those skilled in the art.

FIG. 1 is a perspective view of a heat sink 10 according to one embodiment of the present invention. The heat sink 10 includes a heat sink base 20 having a periodic pattern structure and a cooling fin structure 40 coupled to the heat sink base 20. A mounting tab 16 is provided that attaches the heat sink 10 to a circuit board (not shown) or otherwise secures the heat sink in thermal communication with a heat generating component such as an integrated circuit. A continuous electrically conductive circuit board layer 14 is also shown, with the remainder of the circuit board omitted for clarity. The continuous electrically conductive layer 14 is a very thin, usually metal layer of the circuit board, such as the ground plane of the circuit board or the power supply plane, also referred to herein as the metal layer 14. The heat sink base 20 and the metal layer 14 having a periodic pattern collectively form an EBG structure which will be described further below.

The metal layer 14 also defines a convenient reference plane for describing some physical features of the heat sink 10. Both the first surface 22 of the heat sink base 20 and the second surface 24 located on the opposite side thereof are parallel to the metal layer 14. For this particular embodiment, the first and second surfaces 22, 24 are referred to as the upper surface 22 and the lower surface 24 of the heat sink base 20. FIG. 1 also shows rectangular coordinates (x, y, z) for reference. The “x” axis and the “y” axis represent the two dimensions of the reference plane defined by the metal layer 14. The “z” axis is perpendicular to the x and y axes and is perpendicular to the metal layer 14.

A heat sink base 20 having a periodic pattern is spaced apart and branches 30
The branch 30 defines various openings 29 between the patches 28 including a plurality of patches 28 interconnected by (see FIG. 2). These patches extend upward in the z direction from the reference plane and are spaced from each other in the x and y directions. Patch 28 and branch 30 share a flat upper surface 22 and lower surface 24 located on opposite sides of heat sink base 20. Patch 28 is formed from an electrically conductive / thermally conductive material. Copper is an example of an electrically conductive / thermally conductive material suitable for forming the patch 28.

The cooling fin structure 40 includes a plurality of prong type cooling fins 42 coupled to the heat sink base 20. The cooling fin 42 faces the z direction. That is, metal layer 1
4 extends perpendicularly. Alternatively, other types of cooling fins can be used, but the prong-shaped cooling fins 42 of this embodiment extend transversely across one opening 29 between adjacent patches 28. Without this, it is possible to arrange the cooling fins 42 along the upper surface 22 of the heat sink base 20. The cooling fins 42 are formed from a thermally conductive material such as copper or aluminum, similar to the heat sink base patch 28. The cooling fins 42 are coupled to the upper surface 22 of the heat sink base 20 by a thermally conductive / non-electrically conductive binder 26. In this way, heat is efficiently transferred from the heat sink base 20 to the fins 42 through the bonding material 26, but the cooling fins 42 are electrically isolated from the heat sink base 20 by the bonding material 26.

One example of a material that may be suitable for the thermally conductive / non-electrically conductive binder 26 is an epoxy composite. The components of the epoxy composite can be selected to achieve the desired thermal conductivity, but have a sufficiently low electrical conductivity that can be considered non-electrical conductivity. In this way, the epoxy composite can both securely secure the cooling fins 42 to the heat sink base 20 and electrically insulate the cooling fins 42 from the heat sink base 20. One specific example of a component suitable for imparting thermal conductivity to an epoxy composite is boron nitride, which generally has an electrical conductivity of about 600 W / m · K.

In other embodiments, the thermally conductive / non-electrically conductive binder can be omitted, instead,
The cooling fins 42 can be formed from a thermally conductive / non-electrically conductive material. For example, about 2
Cooling fins can be formed from graphite having a thermal conductivity of 5 to 470 W / m · K and an electrical conductivity of about 50000 S / m.

The number of cooling fins can vary from embodiment to embodiment depending on the size of the heat sink, the desired surface area required for cooling in a particular application, the available space on the motherboard and in the computer housing, and the like. As an example, the cooling fins 42 of this embodiment are grouped into groups of four cooling fins 42 per patch 28. Cooling fin 42
And the length of the cooling fins 42 are selected to provide a sufficient surface area for cooling.
The heat transferred from the heat sink base 20 to the cooling fins 42 can be efficiently removed by air and is usually removed by forced convection, although natural convection can optionally be used.

FIG. 2 is a perspective view of the heat sink base 20 showing in more detail one embodiment of the periodic pattern structure of the heat sink base 20. The cooling fins 42 of FIG. 1 have been removed from the figure to show an array of electrically / thermally conductive patches 28 that are spaced apart and interconnected by branches 30. As an example, the patches 28 are arranged as a rectangular array of 4 rows × 4 columns. Optionally, the array of patches 28 can be equally spaced in the x and y directions. Each branch 30 connects a specific pair of adjacent patches 28.
The openings in the periodic pattern structure between the spaced patches 28 and the branches 30 connecting the patches 28 are indicated generally at 29. More specifically, the opening 29 includes an inner L-shaped slot 31 and an outer open slot 32 along the two outer edges 33 of the heat sink base 20.

Patch 28 and branch 30 are both electrically conductive and thermally conductive. Thus, electrons can freely flow through the heat sink base 20, through the branch 30 and one patch 2.
8 can flow freely to another patch 28. Branches 30 and patches 28 can be formed from the same material, and to obtain the desired pattern of patches 28 and branches 30, a portion of the material is removed, for example, by machining, cutting or etching, Branches 30 and patches 28 can also be formed as a single member, such as when the heat sink base 20 is formed from a single material (eg, copper) block. In this embodiment,
The cross-section 25 of the periodic pattern structure taken parallel to the metal layer 14 can be substantially unchanged in the direction perpendicular to the reference plane. That is, the cross-section can be made generally invariant in the z direction, except for variations within general manufacturing tolerances. The heat sink base 20 has a total heat sink length (LH) and a total heat sink width (WH), and in this embodiment, LH and WH are equal. The heat sink base 20 has a more uniform thickness (t).

Together, the metal layer 14 and the heat sink base 20 having a periodic pattern form an electromagnetic bandgap structure having a characteristic stopband. The stop band mainly depends on the geometry of the periodic pattern structure, including the overall dimensions of the heat sink base 20 and the shapes and dimensions of the patches 28 and branches 30. Since the heat sink base 20 has a uniform thickness, each patch 28 and branch 30 has the same thickness “t”.
Have

FIG. 3 is an enlarged perspective view of a portion of the heat sink base 20 showing the patch 28 and branch 30 geometry in greater detail. In this embodiment, the patches 28 are all the same size, so that each patch 28 has a patch length (L _P ) in the same direction as the length (L _H ) of the heat sink base 20 and the width of the heat sink base 20. (W _H ) and patch width (W _P ) in the same direction. Although not essential, the patch width and patch length are equal (W _P = L _P )
As such, the patch 28 can be square. In order to visually distinguish the patch 28 and the branch 30, the upper surface of the branch 28 is shaded in FIG. 3. Each branch 30 has a branch length (L _B ) along the direction of the interval between adjacent patches 28 to which the branch 30 is connected. That is, the branch 30 connecting two patches arranged at intervals in the x direction has a branch length (L _B ) along the x direction, and the two patches arranged at intervals in the y direction. The branch 30 to be connected has a branch length (L _B ) along the y direction. The patches 28 are arranged at equal intervals with an interval (S) equal to the branch length (L _B ). Since the opening 29 is partially defined by the spacing between the patches 28,
The opening 29 has a width equal to the interval (S) between the patches. As a result of the smaller dimensions of the branch 30 than the patch 28, the branch 30 occupies a much smaller surface area than the patch 28. In one embodiment, each branch 30 has a surface area in the XY plane that is less than about 15 percent of the surface area of that patch for either adjacent patch.

FIG. 4 is a top view of the heat sink base 20 showing the addition of a thermally / non-electrically conductive filler 34 into the opening 29. Since the filler 34 is thermally conductive, heat can be efficiently transferred from the patch 28 to the patch 28 throughout the heat sink base 20. However, since the filler 34 is non-electrically conductive, the presence of the filler 34 causes EB
The electrical characteristics of the G structure are not significantly changed. Since both the binder 26 (see FIG. 1) used to bond the heat sink fins 42 to the heat sink base 20 and the filler 34 need to be thermally and non-electrically conductive, Filler 34 and binder 26 can be selected. For example, using an epoxy compound as the binder 26,
A cooling fin can be coupled to the heat sink base 20 and used as a filler 34 to fill the opening 29 of the heat sink base 20.

FIG. 5 is a dimensioned top view of the heat sink base 20 according to one particular exemplary embodiment. The heat sink base 20 includes three first portions 21 and one second portion 23. FIG. 6 is a dimensioned top view of the first portion 21 of the heat sink base of FIG. FIG. 7 is a dimensioned top view of the second portion 23 of the heat sink base of FIG. The heat sink base 20 of FIG. 5 can be formed from a single piece of material by machining the heat sink base 20 according to the dimensions of FIGS. Alternatively, the heat sink base 20 of FIG. 5 is formed separately with three first portions 21 and one second portion 23, followed by portions 21 and 23 as shown in FIG. It can also be constructed by joining) (by brazing).

FIG. 8 is a side view of an electronic device 50 that includes a heat sink 10 for cooling a microprocessor (“processor”). In this example, the processor is a central processing unit (CPU) 62 on the system board 60. The CPU 62 is disposed in a socket 64 on the system board 60. Prior to securing the heat sink assembly 10 to the system board 60, the CPU 62 is loosely placed in the socket 64. The heat sink 10 is secured at the mounting tab 16 using conventional hardware 17, such as an ungrounded metal post, which securely engages the heat sink base 20 of the heat sink 10 and the CPU 62. Thereby, the heat generated by the CPU 62 is transmitted from the CPU 62 to the heat sink 10. A fan 65 is attached to the system board 60 to generate an air flow through the cooling fins 42 to cool the heat sink 10 by forced convection. Thereby, the heat sink cools the CPU 62.

FIG. 9 is an enlarged detailed view of the part highlighted in FIG. 8 of the electronic device 50. The CPU 62
An electrical contact 66 (such as a land grid array) is aligned with a mating electrical contact 68 on the surface facing the system board 60, and the electrical contact 66 interfaces with the system board 60 by the CPU 62. Make it possible. The metal layer 14 in this example is the ground layer 14 of the system board 60. The CPU is grounded to at least one ground contact 68G. Since the CPU 62 draws a large amount of current, there is a high possibility of generating EMI in the electronic device 50. The core frequency of many ICs (such as CPUs) is often in the same range as the first few resonant modes of the cavity formed by the heat sink base and circuit board reference plane. Therefore, in this case, a cavity resonance effect may occur in a small gap between the heat sink base 20 and the metal ground layer 14. Using conventional heat sinks, this cavity resonance effect amplifies EMI at a specific resonance frequency. However, the embodiment with the periodic pattern of the metal ground layer 14 and the heat sink base 20 together form an EBG structure with a characteristic stop band that reduces EMI at certain frequencies. As described above, the stop band can be adjusted by selecting the heat sink-based physical parameters to achieve the target stop band. The target stopband can be selected, for example, to reduce the peak frequency.

FIG. 10 is a graph 80 showing that the use of a heat sink base 20 according to an embodiment of the present invention having a periodic pattern results in reduced EMI as compared to a conventional solid heat sink base. The graph 80 includes a first frequency plot bounded by the upper curve 81 and a second frequency plot bounded by the lower curve 82. The upper curve 81 represents the frequency response of a frequency range using a solid heat sink base, and the lower curve 82 represents the frequency response of the same frequency range using a heat sink base with a periodic pattern. The original heat sink base is made of copper with a thickness of 0.25 inch (6.35 mm).
It has a 4 × 4 array of 00 mil (12.7 mm) × 400 mil (10.2 mm) patches. The branches connecting the patches were 80 mils (2.03 mm) × 80 mils (2.03 mm). Target stopband regions of about 4 to 5 GHz, 6 to 8 GHz and 10 to 16 GHz are shown. A heat sink-based geometry with periodic patterns and physical parameters were selected to reduce the peak frequency in this frequency range. As clearly shown in graph 80, the use of a heat sink base with a periodic pattern results in a much lower peak frequency as opposed to a conventional heat sink base. Using a heat sink base with a periodic pattern significantly reduces EMI propagation.

In the example of FIG. 10, the target stopband was selected to reduce the peak frequency. However, in a given device, the peak frequency generated by the processor is not necessarily the frequency that most interferes with other circuits. Thus, for all applications, the target stopband need not necessarily include a peak frequency.

FIG. 11 is a flow diagram illustrating an overview of a method according to an embodiment of the present invention for reducing the propagation of electromagnetic noise generated by a processor on a circuit board. Step 100 includes identifying a frequency band of electromagnetic noise generated by the processor. The frequency band to be selected can be selected in consideration of the peak EMI frequency generated by the processor and / or the operating frequency of other devices (especially analog devices) on the circuit board. Step 102 creates a periodic pattern of spaced patches, interconnected by branches, having a geometrical arrangement and physical parameters selected to achieve a target stopband within the identified frequency band. Including selecting. The size, shape and spacing of the conductive patches all affect the actual stopband achieved by the heat sink based periodic pattern structure. This step of selecting a periodic pattern consists of patch width, patch length,
Selecting branch width, branch length, base thickness, or a combination thereof can be included. The general relationship between the physical dimensions of a square EBG structure (ie L _P = W _P ) and the position of the first resonance frequency is given by:
In the above equation, _{A =} W B + _{L P} corresponds to the sum of the dimensions of the gap and the individual EBG elements between individual EBG elements (i.e. width or length). Here, c = 3 · 10 ⁸ m / s, c represents the speed of light in free space, and ε _eff represents the effective dielectric constant of the medium. Assuming W _P = L _P and W _B = L _B taking into account the contribution of the interconnecting branches, this equation is transformed as:
In the case of a rectangular structure, all other subsequent stopband positions can theoretically be determined by substituting L _P for additional lengths of EBG patches and combinations of those lengths. .

In step 104, the heat sink base may be formed according to the periodic pattern selected in step. In step 106, a circuit board having a continuous electrically conductive layer is selected. This formed layer can be a metal layer such as a ground plane or a power plane of the laminated circuit board. The circuit board typically includes a processor and other digital and / or analog circuits. In step 108, a heat sink base having a periodic pattern is secured in thermal contact with the processor. The heat sink base and metal layer having a periodic pattern together form an EBG structure that reduces the amplitude of EMI in a selected stopband frequency range.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular form “
“a”, “an” and “the” are not otherwise clear from the context,
It is intended to include the plural forms. Also, as used herein, the term “comprising” specifies the presence of a specified feature, completeness, step, action, element, component or group, or any combination thereof, It is understood that the presence or addition of one or more other features, completeness, steps, actions, elements, components or groups thereof, or any combination thereof is not excluded. The terms “preferably”, “preferred”, “optional”, “can” and like terms refer to an optional feature (non-essential feature) of the item, condition or step referred to. Used to indicate that

All means or steps recited in the claims below and the corresponding structures, materials, acts and equivalents of the functional elements function in combination with other claimed elements specifically recited in the claims. It is intended to include any structure, material or action to be performed. The description of the present invention has been presented for purposes of illustration and description, but is not intended to be exhaustive or limited to the invention in the form disclosed. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the invention. This embodiment is intended to best explain the principles and practical applications of the present invention, and for those skilled in the art to understand the present invention with respect to various embodiments having various modifications adapted to the particular application contemplated. Selected and explained to make it possible to do.

10 heat sink 14 metal layer, continuous electrically conductive circuit board layer, ground layer, metal ground layer 16 mounting tab 17 bracket 20 heat sink base 21 first part of heat sink base 22 first surface of heat sink base, Heat sink base upper surface 23 Heat sink base second portion 24 Heat sink base second surface, heat sink base lower surface 25 Periodic pattern structure cross section 26 Thermal conductive / non-electric conductive binder 28 Patch ( patch)
29 Opening 30 Branch
31 L-shaped slot 32 Open slot 32
33 Outer edge of heat sink base 34 Thermally conductive / non-electrically conductive filler 40 Cooling fin structure 42 Cooling fin, heat sink fin 50 Electronic device 60 System board 62 Central processing unit (CPU)
64 Socket on system board 65 Fan 66 Electrical contact 68 Paired electrical contact 68G Ground contact 80 Graph 81 Upper curve 82 Lower curve

Claims

A base having a periodic pattern structure including an array of electrically conductive / thermally conductive patches spaced in two dimensions of a reference plane and having a thickness perpendicular to the reference plane;
A plurality of branches structurally connecting the patches, each branch connecting adjacent patches and having a width narrower than the width of each adjacent patch in the reference plane;
A plurality of thermally conductive cooling fins coupled to the base and extending perpendicular to the reference plane;
Including
A heat sink, wherein the base having the periodic pattern structure and the physical parameters of the plurality of branches are selected to achieve a target stopband.
The heat sink according to claim 1, wherein a cross section of the periodic pattern structure is invariant in a direction perpendicular to the reference plane.
The heat sink of claim 1, further comprising a thermally conductive / non-electrically conductive filler that fills a space between the adjacent patches.
The heat sink of claim 1, wherein the patch has an electrical conductivity of at least 10 ⁷ S / m and a thermal conductivity greater than 1 W / m · K.
The heat sink of claim 1, further comprising a thermally conductive / non-electrically conductive binder that couples the cooling fin to a surface of the base.
The heat sink of claim 1, wherein the cooling fin is thermally conductive and non-electrically conductive.
The heat sink of claim 1, wherein each branch has a surface area within the reference plane that is less than about 15 percent of the surface area of the patch for either of the adjacent patches.
The heat sink of claim 1, wherein the periodic pattern structure and the branches share first and second common surfaces located on opposite sides of each other.
A printed circuit board comprising a continuous electrically conductive layer;
A processor physically coupled to the printed circuit board and electrically coupled to the electrically conductive layer;
A heat sink coupled to the circuit board in thermal contact with the processor;
A base having a periodic pattern structure including an array of electrically conductive / thermally conductive patches, wherein the heat sink is spaced parallel to the conductive layer and has a thickness perpendicular to the conductive layer; A plurality of branches structurally connecting the patches, each branch extending across an opening between two adjacent patches, and having a width narrower than a width of each adjacent patch in a reference plane A plurality of branches and a plurality of thermally conductive cooling fins coupled to the base and extending perpendicular to the reference plane;
An apparatus in which the base having the periodic pattern structure and the physical parameters of the plurality of branches are selected to achieve a target stopband.
The apparatus of claim 9, wherein the conductive layer of the printed circuit board is a ground plane.
The apparatus of claim 10, further comprising a plurality of metal columns that secure the processor to the circuit board, wherein the metal columns are not grounded to a ground layer.
Further comprising a thermally / non-electrically conductive binder that couples the cooling fin to the base;
The apparatus according to claim 9.
The apparatus of claim 9, wherein the periodic pattern structure has a substantially invariant cross section taken parallel to the reference plane.
The apparatus of claim 9, further comprising a thermally / non-electrically conductive filler that fills a space between the adjacent patches.
The apparatus of claim 9, wherein the patch has an electrical conductivity of at least 10 ⁷ S / m and a thermal conductivity greater than 1 W / m · K.
The apparatus of claim 12, wherein the thermally conductive / non-electrically conductive binder comprises an epoxy resin.
Each branch is about 1 of the surface area of the patch for either of the adjacent patches.
The apparatus of claim 9 having a surface area of less than 5 percent.
The apparatus of claim 9, wherein the periodic pattern structure and the branches share a first and second flat common surface located on opposite sides of each other.